ETS1 is a transcription factor capable of binding to purine rich core motif (-GGAA-) present in the promoter/enhancer regions of many cellular and viral genes. ETS1 is expressed at high levels in lymphoid cells. Blocking the formation of ETS1 in Jurkat T-cells increases their ability to produce Interleukin-2. To elucidate the role of ETS1 in T-cells, we have expressed mutant forms of ETS1 in Jurkat T-cells and obtained several stable cell lines. Jurkat T-cells expressing ETS1 DNA binding domain (lacking transcriptional activities) remain at G0/G1 stage for a longer time and upon activation, produce lower amounts of lymphokines. Experiments are in progress to identify the cellular target genes for ETS1. ERGB/FLi1 is a member of the ets family of transcription factors. ERGB/FLi1 gene expression is higher in peripheral blood mononuclear cells from lupus patients than from healthy individuals. Its expression correlates with the aggressiveness of the disease. ErgB/Fli1 but not Ets1 gene expression is higher in splenic T-cells from autoimmune-prone mice than from normal mice. ErgB/Fli1 gene expression is also high in salivary glands from human T-cell leukemia virus Tax1 transgenic mice than the normal mice. Experiments are in progress to find out if ErgB/Fli1 could be used as a marker for autoimmune disease and to understand its role in T-cell proliferation and activation processes.